An immune system comprises a network of molecules and cells designed for a singular purpose, namely, to distinguish between self and nonself. As a protector against viral, bacterial, and parasitic pathogens, the immune system relies on two strategies to react to countless molecular entities and initiate destruction of the entities identified as foreign bodies. The first strategy is the humoral immune response, dedicated to a recognition role through plasma cell-derived antibodies. The second strategy is the cellular immune response, dedicated to the eradication of cells displaying foreign motifs on their surfaces.
Local immuno-inflammatory processes involve a series of changes that include at least three steps: 1) peripheral blood leukocytes adhere to the endothelial wall and become fully activated; 2) the leukocytes migrate toward the inflammatory site; and 3) phagocytosis and, eventually, bacterial killing takes place. These processes are mediated by molecules known as selectins and integrins (Springer, 1995). CD11b is an integrin that is particularly relevant in bacteria-induced inflammatory processes. It is constitutively expressed on phagocytes, T- and B-cell subsets and natural killer (NK)/cytotoxic cells in several species (McFarland et al., 1992; Muto et al., 1993; Ross et al. 1993; Hasslen et al, 1996).
CD11b has at least three major functions in association with leukocytes. In lymphocytes, it is required for adhesion to the endothelium (Buysmann et al., 1997), then it is required for migration, and later, it mediates adhesion to parasites (Forsyth et al., 1996; Forsyth et al., 1997). In phagocytes, CD11b mediates diapedesis of leukocytes through the endothelium via generation of a high-affinity binding site for intercellular adhesion molecule-1 (Hogg et al., 1995; Sugimori et al., 1997). CD11b also mediates phagocytic and degranulation responses to bacteria or immune complexes opsonized with iC3b (Petty et al., 1993; Sutterwala et al., 1996). Most of the CD11b contained in leukocytes is not expressed on the membrane, but is stored in intra-cytoplasmic granules. Upon stimulation with cytokines (IL-1, TNF-xcex1), cell activating agents such as endotoxin, bacteria, or parasites induce an increase in CD11b expression, derived from intra-cytoplasmic CD11b (Ross et al., 1993; Hasslen et al., 1996). Not surprisingly, increases in CD11b receptor density have been reported in inflammatory diseases (Tsutsui et al., 1999). In S. aureus infections, expression of CD11b is positively correlated with bacterial clearance (Gordon et al., 1989; Inoue et al., 1998) and it has been shown that CD11b contains multiple sites for binding microbes (Ross et al., 1985).
CD11b is a molecule essential in leukocyte activation, leukocyte migration from peripheral blood or tissue to the inflammatory site, and phagocytosis (Ross et al., 1985; Petty and Todd, 1993; Hogg and Berlin, 1995). The use of fluorescent beads allows for flow cytometric evaluation of phagocytosis (Miyauchi et al., 1998). In addition, flow cytometry can quantify the number of each leukocyte type based on scatter light measurements. Inoculation of viable, but not infective, S. aureus into the peritoneum induces a local inflammation which results in a cell infiltrate collectable through peritoneal lavage.
Lymphocytes differ functionally over their lifetime. While thymic and peripheral blood T-lymphocytes are regarded as unprimed or naive cells (i.e., cells not exposed to foreign substances such as invading bacteria), lymphocytes found at local sites (i.e., mammary gland) are xe2x80x9cmemoryxe2x80x9d or xe2x80x9ceffectorxe2x80x9d cells that have been exposed to specific foreign antigens and are permanently capable of responding to them. This difference is reflected in the lymphocyte phenotype: unprimed or naive cells are predominantly CD45r positive (higher receptor density per cell) while memory or effector cells are predominantly CD45r negative (Taylor et al., 1994).
Bovine mastitis is typically a local inflammatory process of the udder associated with bacterial invasion, and Staphylococcus aureus is one such etiologic agent. While prevention or decreased prevalence of bovine mastitis would be facilitated by enhancing a local immune response, testing of putative immuno-modulatory therapies is frequently limited by the cost and logistical needs of in vivo studies. Thus, development and evaluation of new models of bovine mastitis is a pre-condition for selection of products that later may be evaluated in the bovine species, as well as for potency monitoring of products used to prevent bovine mastitis.
Validation of successful models must fulfill several conditions. First, a desirable model should include variables directly relevant to those present in bovine mastitis. One such set of variables comprises indicators of leukocyte activation, migration, and phagocytosis. Second, a model and its procedures should be accurate, repeatable, economical and capable of being rapidly tested. While in vitro models may meet several criteria, in certain circumstances they lack variables of biological relevance. However, the goal of biological relevance and the criteria indicated are met through the implementation of an in vivo model.
The present invention relates to a composition and method for non-specific enhancement of immune responses. A colostrum-derived dietary supplement (CDDS) is described for human or veterinary use. CDDS comprises a sprayed-dried preparation of pasteurized and homogenized first milking colostrum that when administered orally enhances immune responses in a recipient human or animal. Generally, CDDS is administered in a conditioning dose once per day during a conditioning period of time from about 7 to 14 days, and then in a maintenance dose administered once per day during a period that follows the conditioning period. The maintenance dose is about one-half the concentration of the conditioning dose. Administration of CDDS enhances the immune response in a recipient in a dose-dependent manner, and has been shown to effectively result in an increase in the expression of CD11b positive receptors on blood lymphocytes, an increase in CD11b receptor density on blood lymphocytes, an increase in the expression of CD4 positive receptors on lymphocytes, enhancement of leukocyte activation in a recipient, an increase in phagocytic function in macrophage cells, an increase in phagocytic function in polymorphonuclear (PMN) cells, an increase in the expression of activated PMN cells, and an increase in the expression of CD11b positive PMN cells.
The present invention will become apparent to those skilled in the art upon reference to the following specification, figures, and claims.